Demand for an electrochemical device such as a lithium ion secondary battery having a high energy density and capable of being charged and discharged repeatedly has been rapidly increased by taking advantage of characteristics thereof. The lithium ion secondary battery is used in a field of a cellular phone, a notebook type personal computer, an electric car, or the like because of a relatively large energy density.
The lithium ion secondary battery is a secondary battery in which an electrode constituent body obtained by laminating or winding a positive electrode member, a separator member, and a negative electrode member is housed in an outer casing. In recent years, the lithium ion secondary battery has been spread widely, while a capacity thereof has become larger, and improvement of a capacity density has been required. Particularly, improvement of a weight density has been requested strongly. Therefore, due to a request for a lighter weight, a pouch-type battery obtained by enclosing an electrode constituent body in a container having a laminated film outer casing with a heat-sealed end has been proposed in place of a metal outer casing.
In the pouch-type battery using a laminated film outer casing, fixing is performed by inserting tabs which are metal plates for extracting electricity to the outside and are connected to a positive electrode current collector and a negative electrode current collector as a part of an electrode constituent body into an outer casing, and bonding the tabs to a heat-sealing portion of the outer casing closely, but the electrode constituent body itself is not fixed to the outer casing.
Here, conventionally, in a case of a small battery used for a portable electronic device, an electrode constituent body included in a laminated film outer casing has a small weight, and the electrode constituent body does not move easily when vibration is applied thereto from an outside. Therefore, a force applied to the tab portion does not change sealing performance.
However, a battery for a portable electronic device has increased the capacity thereof and the size thereof. Furthermore, in a large battery used for an electric car or the like, an electrode constituent body housed in a laminated film outer casing has a large weight, and therefore the electrode constituent body easily moves when vibration is applied thereto. Accordingly, the force applied to the tab portion is increased, adhesiveness between the tab portion and the outer casing is lowered, and sealing performance may be thereby lowered.
Patent Literature 1 has proposed use of an adhesive tape having an adhesive layer on one surface of a substrate for winding stop of a wound battery. However, the tape has no adhesiveness to a portion other than an adhesive surface, and is not suitable for fixing an electrode constituent body to an outer casing.
Patent Literatures 2 and 3 describe use of a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both surfaces of a substrate for fixing an electrode constituent body to an outer casing in a battery. Patent Literature 3 has further proposed use of a releasable sheet on an adhesive surface of an electrode constituent body having a double-sided adhesive tape pasted thereon before the electrode constituent body is enclosed in order to prevent a problem such as occurrence of adhesion at an entrance when the electrode constituent body is enclosed in an outer casing of a battery. However, when the releasable sheet is peeled off and the electrode constituent body is bonded to the outer casing, air bubbles remain between the adhesive tape and the outer casing, an adhesive force is poor particularly after storage at a high temperature, and a capacity retention ratio of an obtained lithium ion secondary battery after storage at a high temperature is not sufficient.
Patent Literature 4 discloses an adhesive tape obtained by applying an acrylic or silicone adhesive to a film such as a biaxially oriented polypropylene film. However, both surfaces thereof are adhesive surfaces made of the same material, and therefore it is not possible to satisfy both preventing unwound of an electrode constituent body and fixing thereof to an outer casing.